There has been conventionally known an electret power generating element (hereinafter simply referred to as “power generating element” as well) that converts vibration energy into electric energy using an electret material. The electret material is a dielectric in which dielectric polarization remains even if an electric field is eliminated as in magnetic polarization of a permanent magnet.
Patent Literature 1 describes a power generating element including a first electrode including an electret material and a second electrode made of metal. In this power generating element, the first electrode or the second electrode elastically moves in an XY plane and a charge amount electrostatically induced to the second electrode changes, whereby electric energy is extracted to the outside of the power generating element.